1. Field of the Invention
The present invention relates to testing and measurement devices, and particularly to a system and method for measuring rolling resistance during pre-rolling, and more particularly, to a system and method for measuring the moment of forces of resistance, dimensionless coefficients of rolling friction, and the hysteretic losses on both uncoated and coated surfaces.
2. Description of the Related Art
Rolling resistance, sometimes referred to as “rolling friction” or “rolling drag”, is the resistance that occurs when a round object, such as a ball, tire, or wheel, rolls on a surface. The rolling resistance is primarily caused by the deformation of the object, the deformation of the surface, and movement below the surface. Additional contributing factors include wheel diameter, forward speed, the load on the wheel, surface adhesion, sliding, relative micro-sliding between the surfaces of contact, and their roughness. The rolling resistance greatly depends on the material of the wheel or tire and the type of ground or other surface. What might be termed “basic rolling resistance” is steady velocity and straight line motion on a level surface, but there also exists rolling resistance when accelerating, when on curves, and when on a grade.
Rolling resistance may be defined as the moment a rolling force) needed to overcome resistance to rotation and to move forward. The rolling resistance is much smaller than the sliding friction between two surfaces under equal loads, typically by a factor of at least one hundred. During the rolling process, it is possible for micro-slip to occur in a region within the contact area, inducing loss of mechanical energy through friction, thus leading to hysteresis loss and non-local memory, as is observed in pre-rolling. Rolling slowly from rest exhibits increasing rolling resistance, which starts from zero to steady-state rolling with constant rolling resistance. In this range of pre-rolling, the rolling resistance has a non-linear behavior. The pre-rolling stage induces hysteresis, which is typically difficult to measure due to its non-linearity.
In rolling friction, two separate stages must be considered. The first stage is the pre-rolling stage, in which the deformation forces are dominant and the patch contact includes sub-regions of adhesion and slip. The second stage is the steady rolling stage in which the rolling resistance has been fully developed to its maximum value and has more pronounced rotation.
The linear and large-scale steady rolling stage is relatively easy to describe and measure. The pre-rolling stage, however, not only includes non-linear considerations, but occurs only on a very small scale of pre-movement. Thus, it would be desirable to be able to easily make measurements of rolling resistance during the pre-rolling stage.
Thus, a system and method for measuring rolling resistance solving the aforementioned problems is desired.